Compact binary systems in scalar-tensor gravity. III. Scalar waves and energy flux

• Main Author: Lang, Ryan N
• Format: Journal Article
• Language: English
• Published: 08-05-2015
• Subjects: Physics - General Relativity and Quantum Cosmology
• DOI: 10.48550/arxiv.1411.3073

Phys. Rev. D 91, 084027 (2015) We derive the scalar waveform generated by a binary of nonspinning compact
objects (black holes or neutron stars) in a general class of scalar-tensor
theories of gravity. The waveform is accurate to 1.5 post-Newtonian order
[$O((v/c)^3)$] beyond the leading-order tensor gravitational waves (the
"Newtonian quadrupole"). To solve the scalar-tensor field equations, we adapt
the direct integration of the relaxed Einstein equations formalism developed by
Will, Wiseman, and Pati. The internal gravity of the compact objects is treated
with an approach developed by Eardley. We find that the scalar waves are
described by the same small set of parameters which describes the equations of
motion and tensor waves. For black hole--black hole binaries, the scalar
waveform vanishes, as expected from previous results which show that these
systems in scalar-tensor theory are indistinguishable from their general
relativistic counterparts. For black hole--neutron star binaries, the scalar
waveform simplifies considerably from the generic case, essentially depending
on only a single parameter up to first post-Newtonian order. With both the
tensor and scalar waveforms in hand, we calculate the total energy flux carried
by the outgoing waves. This quantity is computed to first post-Newtonian order
relative to the "quadrupole formula" and agrees with previous, lower order
calculations.